UC Berkeley explosion outside California Hall

US Berkeley explosion: The explosion on the UC Berkeley campus Monday night occurred at a utility vault after a power outage as crews were working to restore power. One person was hospitalized with minor burns.

Fire and smoke pour from a utility vault after an explosion on the University of California Berkeley campus on Monday, Sept. 30, 2013 in Berkeley, Calif.

(AP Photo/The Daily Californian, Kelly Fang)

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Berkeley, Calif.

The University of California at Berkeley campus was evacuated after a power outage cancelled evening classes and an explosion that led to one person being hospitalized for minor burns.

The explosion occurred in an underground utility vault outside California Hall as crews were trying to restore power on campus shortly before 7 p.m. Monday. In addition to the one person hospitalized, three others also received minor burns but refused treatment, said UC Berkeley spokesman Dan Mogulof.

With many buildings in the dark, fire crews also freed about 20 people stuck in dormitory elevators as a result of the outage that also led to the mandatory evacuation on campus.

Tuesday morning, the UC Berkeley Twitter account reported that power had been restored to most of the campus, but some classes were canceled.

"I have midterms tomorrow as do a bunch of other students on campus. A lot of students don't have power to study or get their laptops on or anything like that," Kelsie Carlson, a freshman, told KTVU-TV Monday evening.

The power outage was reported around 4:30 p.m. Monday and led to evening classes being canceled as students were told to suspend all lab activities, Mogulof said.